This invention relates to gratings to allow or impede flow of hearing or air conditioning into a room.
In a first aspect the gratings with which the invention comprise a stationary and a slidable grid. The slidable grid is adapted to move between a limit position allowing a substantial air passage, and known as the OPEN position and a position blocking substantial air passage known as the CLOSED position. Control will customarily be by thermostat as hereafter described.
In a second aspect, a surface grating which faces upwardly is shaped to define a recessed shape to receive an upper or third grating. The upper grating will sit on a filter held by the recessed shape for application use and replacement, the recessed arrangement described is found to provide best filter use so far encountered.
With this recessed arrangement shown, the filter is held in place by the upper grating which may be removed to change, insert or remove a filter. This is the most efficient filter arrangement yet devised.
The first aspect of relatively movable grids may be and the second aspect of recessing the upper shape of the grating may of course be present in the same device or may be singly present in different devices.
The slidable grid will preferably be constructed so that there are no positions between OPEN and CLOSED limiting position so that the grid merely moves between these limiting positions. Preferably a motor is connected to drive the movable grid between limiting positions. The motor is controlled by a thermostat.
The preferred principle of operation is that the movable grid may be called for to move to an OPEN position as ( in the winter ) the thermostat calls for a warmer temperature and CLOSE when the thermostat calls for cooler temperature. (In the summer the OPEN and CLOSED positions correspond to respective desires for cooler and warmer temperatures.) It is found easier herein to describe the winter thermostat and to refer briefly to the opposite summer settings. Accordingly, in the winter if the movable grating is closed the circuitry for the motor is arranged so that the contact is closed which will turn the motor to move to open grating position when the thermostat calls for warmer temperatures. Thus when the grating reaches open position the associated controls close the contacts ready to move the grating back to closed as soon as the thermostat calls for cooler temperatures. In a preferred form of the invention the end of a movement to open or closed position cuts all power to the drive circuit avoiding motor loss and extra safety controls.
Since in the preferred arrangement, the movable grid moves between limiting positions and requires no power at the limiting positions, there is a great saving with the inventive arrangement since the power and the control circuit are disconnected from the power after each change of limiting positions.
There are a great many ways that the movable grid may be thus controlled and these are all considered within the scope of the invention.
The use of one or more thermostatically controlled gratings is believed to create great fuel savings in heating costs (or in summer, cooling) costs. For a number of gratings in one room may be run to be controlled movable to be powered in parallel under the control of a single thermostat. It is found that the thermostat control may carry enough current that four or five motors for movable grating control may be powered by the current carried by a single thermostat.
I prefer to achieve the drive by a motor rotatable in one direction and driving a cam which over one 180xc2x0 rotation will contact a stop for the movable grid for OPEN to CLOSED position.
A resilient yieldable aim is preferably provided whereby if there is resistance to the movable grid movement, such movement will merely stress the aim and the movement will not be completed until the cause of the resistance is removed. This provides a useful safety feature since for example fingers stuck in a closing grating will not be crushed
In a preferred form of the invention the motor drives the movable grid between OPEN and CLOSED positions whether in a 180xc2x0 half cycle as previously discussed or otherwise, and then is adapted to operate a cam to shut off the motor power at each limiting position. The cam connects a switch in the motor control circuit so that the motor is ready to drive the movable grating in the other direction, but does not because the thermostat is not then calling for the movement, leaving that part of the circuit open.
In a preferred form of the invention the motor for driving the movable grid is connectable for rotation through one of two alternate circuits. One of the alternate circuits is adapted to power the motor during travel from CLOSED to OPEN position and the other to power the motor during travel from OPEN to CLOSED positions. A cam operable by the motor controls an arm setting operable on arrival at CLOSED position to set the arm to break power in the closing circuit (thus cutting all power to the motor) and at the same time setting the cam to connect the motor to be ready to power the opening circuit when later called for by the thermostat.
Thus there are two circuits for the motor. The normally closed circuit contacts are preferably connected in series with the warm limit contact of the thermostat and the normally open circuit is preferably connected in series with the cool limit contact.
Thus in the winter with the grating full OPEN for maximum air flow, the motor cam is positioned to complete the circuit to close the grid when there is a call for a cooler temperature.
Thus when the thermostat temperature is at the warm limit caused it completes the motor circuit to close the grating.